Currently, hand-held heat sources, capable of producing heat at a sufficiently high temperature to activate heat-shrink material, rely on either the combustion of flammable material or electrical power to provide energy for generating the required heat. The use of heat-shrink material to insulate and protect splices in electrical and electronic cables is developed technology. Repairs, using this technology, to electrical and electronic wiring in aircraft are frequently made in areas where no ready source of electrical power of suitable voltage to operate approved heat producing devices is available. Because of the presence of oxygen, fuel and other flammable or explosive equipment, any device used in an aircraft must be constructed so as not to produce any open flame or electrical spark. The use of non-approved electrical heat producing devices is not permissible for reasons of personnel safety as well as possible damage to or destruction of the aircraft. Lack of suitable power at the repair site often precludes the use of approved devices.
The use of combustion heat sources is not acceptable due to the risk of fire or explosion caused by an open flame in a confined space where an explosive atmosphere may exist and the lack of uniformity of heat dispersion. It is particularly desirable to have the heat applied evenly to heat-shrinkable tubing so that the tubing shrinks uniformly around the splice without burning the tubing. While some operators have acquired a high degree of skill in applying the heat from combustion heaters to the surface of heat shrinkable material, with such high localized temperatures heat shrinkable tubing is easily burned thus limiting the effectiveness of the sealing and insulation characteristics of the tubing. No matter how skilled an operator becomes the use of combustion heaters in confined areas where an explosive atmosphere may exist is foolhardy.